The present invention relates to a color image formation apparatus, a tandem color image formation apparatus and an image formation apparatus, which use multiple latent image substrates. For example, the invention relates to image formation apparatuses such as copiers, printers, facsimile machines, and the like.
Conventionally, a color image formation apparatus, wherein toner images formed on multiple photosensitive bodies are sequentially transferred onto a single sheet of transfer paper such that the images are superimposed to obtain a color image, is known as disclosed for example in Japanese Patent No. 2677566.
In the conventional color image formation apparatus, a so-called tandem image formation unit, wherein image formation sections, each comprising a photosensitive body for a color, are arranged in conveyance direction of the transfer paper, and a transfer unit comprising a transfer belt, are both placed horizontally. Further, a paper-feed tray is placed on a side of the image formation unit and the transfer unit.
According to such a conventional color image formation apparatus, color toner images formed on multiple photosensitive bodies are superimposed on the transfer paper to obtain the color image.
In the above conventional tandem color image formation apparatus, since the image formation unit is placed horizontally and the paper-feed tray is placed on the side of the image formation unit, lateral breadth of the apparatus becomes wide and it has been desired to reduce more space required for installation of the apparatus.
There is, for example, an image formation apparatus disclosed in Japanese Laid Open Patent No. 11-95520, which is downsized by reducing the breadth of the apparatus. In the apparatus, multiple laser scanning units are stacked partially overlapping each other, and multiple image formation devices plus a transfer unit arranged opposite to the devices are placed diagonally. This structure enables reduction in breadth of the image formation section and breadth of the whole apparatus.
Recently, needs for image formation on both sides of paper have increased, and more apparatuses are equipped with a mechanism for reversing the sides of the paper. The apparatus disclosed in Japanese Laid Open Patent No. 11-95520 is also provided with a switchback conveyance path for reversing the paper, and re-feeds the paper to the image formation section after leading the paper passed through a fixing device to this switchback conveyance path and reversing the sides of the paper.
There are also image formation apparatuses such as copiers, printers, facsimile machines, and the like, wherein: a recording material is held on a belt that is rotary-driven; and a transfer conveyance belt device for transferring the developed image, formed on an image substrate, onto the recording material while conveying the recording material in accordance with rotation of the image substrate. Generally, these apparatuses have a structure wherein the recording material is fed to the image substrate and a transfer section that is in the transfer conveyance belt device, with a timing adjusted with a resistant unit such as resistant rollers or the like.
An image formation apparatus is also disclosed, wherein a transfer conveyance belt device is placed diagonally (in such a way that heights of an inlet and an outlet for a recording material are different) and a paper conveyance path is shortened, to reduce time needed for printing.
In this image formation apparatus, there are several ways of paper-ejection such as a paper-ejection tray provided on top face of the apparatus or on a side of the apparatus. For printers, for example, paper-ejection trays are provided on top of the apparatus to enable page collation.
On the other hand, many copiers eject paper to a side of the copier main body since they are equipped with a scanner, and/or an ADF (automatic document feeder) on top of the copier. When a duplex mechanism is provided in printers or copiers, the fixed paper is conveyed downward in some cases. As explained above, ways of conveying the fixed paper vary with the structure of the image formation apparatus.
In the conventional tandem color image formation apparatuses, although it is attempted to reduce volume of the apparatus by placing the image formation unit diagonally, the breadth is still large as the paper-feed tray is placed on the side, and further reduction in space required for the installation has been demanded.
In the apparatus disclosed in Japanese Patent Application Laid Open No. 11-95520, since the switchback conveyance path has a structure wherein the paper is conveyed in two horizontal directions to reverse the sides of the paper, breadth of the paper reversal section is wide. In other words, in the apparatus, a section that practically reverses the paper is the switchback conveyance path, and the paper is reversed in the section that is less than half the breadth of the whole apparatus. Therefore, if faces, of a large paper such as an A3 paper in a lengthwise direction, are to be reversed, the breadth of the apparatus must be wide. If the breadth of the apparatus is reduced too much, reversal of large paper becomes impossible.
In such conventional image formation apparatuses downsized by reducing the breadth of the apparatus, the reduction in the breadth of the image formation section is not turned to advantage, as the breadth of the paper reversal mechanism section has to be widened, even if the image formation device and the transfer unit are placed diagonally to reduce the breadth of the image formation section.
In the conventional image formation apparatuses having a structure wherein the transfer conveyance belt device is placed diagonally, when the fixing device is placed diagonally in accordance with the paper conveyance direction directed by the transfer conveyance belt device, the paper ejection direction of the fixing device becomes diagonal, and creates a problem that it can be both advantageous and disadvantageous in terms of compatibility of the apparatus to the above-described different directions of paper conveyance.
For example, when the paper is to be conveyed to the paper-ejection tray on top of the apparatus, ejection of the paper diagonally upward from the fixing device that is placed diagonally is preferable, in terms of paper conveyance. However, if the paper is to be fed to the duplex mechanism that is placed below the fixing device, the conveyance direction of the paper ejected diagonally upward from the fixing device that is placed diagonally has to be altered greatly, and this will increase length of the conveyance path and thus the space required for the apparatus.
Thus, even when the transfer conveyance belt device is to be placed diagonally, the apparatus may be made to correspond to various conveyance directions by providing the fixing device horizontally. For example, in an apparatus disclosed in Japanese Laid Open Patent No. 8-87151, although the transfer conveyance belt device is placed diagonally (in an embodiment of the apparatus, diagonally from the top to the bottom), the fixing device is placed horizontally. However, in the embodiment, the conveyance direction of the paper fed out from the transfer conveyance belt device is to be changed with a guide plate at an entrance of the fixing device. According to such a structure, the paper is bent as the paper, holding a toner image to be fixed, is slidingly scraped on the guide plate when the conveyance direction of the paper is altered. As a result, the unfixed toner image on the paper may be damaged.
According to the structure wherein the recording material is fed out to the image substrate and the transfer section of the transfer conveyance belt device with the timing adjusted by the above-described conventional resistant unit such as resistant rollers, the conveyance of the recording material may be affected during a process of delivering the recording material to the transfer conveyance belt device from the resistant rollers. For example, if the recording material is firm, at an instant when a trailing end of the recording material comes out of the resistant rollers, a slight vibration is caused, and as a result a problem occurs wherein a variation in the image position against the recording material is caused. In the color image formation apparatus wherein multiple images differently colored from each other are sequentially superimposed onto a sheet of paper, this problem leads to a big problem that the image obtained becomes out of color registration.
It is a first object of the present invention to provide a color image formation apparatus and a tandem color image formation apparatus wherein reduction of space required for the apparatus can be achieved.
Further, it is a second object of the present invention to provide a color image formation apparatus and a tandem color image formation apparatus wherein reduction of apparatus volume can be achieved with reduction in the breadth of the apparatus even when the apparatus is equipped with a paper reversal mechanism.
Further, it is a third object of the present invention to provide an image formation apparatus: wherein the problems associated with the image formation apparatus comprising the transfer conveyance belt device that is placed diagonally are solved; which is compatible with the various ways of paper conveyance following the fixing process; and wherein the unfixed toner image on the paper is not damaged before the fixing process.
Further, it is a fourth object of the present invention to provide an image formation apparatus wherein the above-explained problems associated with the conventional image formation apparatus are solved, and the adverse effects on the recording material that is conveyed on the transfer conveyance belt device are prevented.
The invention relates to a color image formation apparatus for forming a color image comprising an image formation unit, which is placed diagonally in relation to a vertical direction, a largest paper-feed tray which is placed below the image formation unit and feeds paper toward image formation sections of the image formation unit, a small-size paper-feed tray which is placed below the image formation unit and above the largest paper-feed tray, and feeds paper toward the image formation sections of the image formation unit.
Further, the invention is a tandem color image formation apparatus comprising an image formation unit wherein three or more colors of respectively independent image formation sections are placed parallel along the paper conveyance direction and diagonally in relation to a vertical direction, a largest paper-feed tray which is placed below the image formation unit and feeds paper toward the image formation sections of the image formation unit, and a small-size paper-feed tray which is placed below the image formation unit and above the largest paper-feed tray, and feeds paper toward the image formation sections of the image formation unit.
Further, the invention relates to a color image formation apparatus, which is capable of duplex printing, comprising an image formation unit which is placed diagonally in relation to a vertical direction, a paper-feed section which is placed below the image formation unit and feeds paper toward image formation sections of the image formation unit, a transfer unit which is placed parallel and opposite to the image formation unit, a duplex reversal unit which is placed on a side of the apparatus, and reverses sides of transfer paper, along the vertical direction, after the paper is passed through the transfer unit, and a duplex conveyance unit which is placed below the transfer unit and re-feeds the reversed transfer paper toward the image formation sections.
Further, the invention is a tandem color image formation apparatus comprising an image formation unit wherein three or more colors of respectively independent image formation sections are placed parallel along paper conveyance direction and diagonally in relation to a vertical direction, a paper-feed section which is placed below the image formation unit and feeds paper toward the image formation sections of the image formation unit, a transfer unit which is placed parallel and opposite to the image formation unit, a duplex reversal unit which is placed on a side of the apparatus, and reverses sides of transfer paper, along the vertical direction, after the paper is passed through the transfer unit, a duplex conveyance unit which is placed below the transfer unit and re-feeds the reversed transfer paper toward the image formation sections.
Further, the invention provides an image formation apparatus comprising an image substrate, a transfer conveyance belt device that is placed opposite to the image substrate, and a heat fixing device, wherein the transfer conveyance belt device is placed diagonally in such a manner that height of a recording material inlet is different from that of a recording material outlet, and wherein conveyance direction of the recording material conveyed by the transfer conveyance belt device is altered at a fixing nip of the heat fixing device before the recording material is ejected from the fixing device.
Further, the invention relates to an image formation apparatus comprising an image substrate, a transfer conveyance belt device which is placed opposite to the image substrate, a resistant unit which conveys a recording material to the transfer conveyance belt device with a timing adjusted in accordance with a position of an image on the image substrate, wherein multiple image substrates are placed parallel and opposite to the transfer conveyance belt device and formation of a color image is possible by transferring the images formed on respective image substrates onto the recording material that is conveyed by the transfer conveyance belt device such that the images are superimposed, and the transfer conveyance belt device is configured in such a manner that its posture can be controlled, and in a color mode, the posture of the transfer conveyance belt device is controlled to make the conveyance direction of the recording material directed by the transfer conveyance belt device approximately equal to that directed by the resistant unit.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.